The present invention relates to providing a continuously variable electrical signal from a transducer indicating the relative position of an object with respect to a stationary reference. In particular, the invention relates to providing an electrical signal indicative of the angular position of a magnet disposed on the object with respect to the stationary reference. Devices of this type are particularly desirable for indicating the relative position of the magnet and the object and find application in linear and rotary position sensing devices.
It is known to provide a magneto resistive sensor for indicating the position of a magnet moving with an object; and, such a sensor is that produced by the Honeywell Corporation and bearing manufacturer designation HMC1512.
Referring to FIG. 4, the electrical output of a known sensor is shown wherein the voltage wave is plotted as a function of the rotary position xcex8 in degrees and indicates the phase difference of 45xc2x0 for the functions SIN 2xcex8 and COS 2xcex8, with a period of 180xc2x0 (xcfx80 radians) for the voltage wave output of the transducer.
However, it has been desired to provide a rotary position transducer having a linear voltage output with respect to the rotary position of the magnet with respect to the stationary sensor. A linear output has the advantage that the output voltage may be used to drive directly an indicator such as a volt meter to give an easy-to-read indication to the user of the rotary position of the object.
The present invention provides a method for linearizing the output of a motion detecting transducer having a dual wave form output in the form of a sine and cosine wave voltage. The linearization is accomplished by piecing together and inverting where necessary the substantially linear portion of the sine and cosine waves of the transducer output voltage. An amplifier and multiplexer function are utilized to provide an analog output of substantially linearly varying voltage as the transducer detects motion of an object moving with respect to the stationary transducer. The moving object has a magnet associated therewith; and, the change in angular bearing of the object is measured by a transducer and the transducer voltage wave form segmented and pieced together in accordance with a predetermined set of conditions for each segment as the angle of bearing changes from zero to 180xc2x0.